/Engine/Plugins/Online/OnlineSubsystem/Source/Public/Interfaces/OnlineUserInterface.h
Get the cached user ids for the specified external ids
void GetExternalIdMappings ( const [FExternalIdQueryOptions](API\Plugins\OnlineSubsystem\Interfaces\FExternalIdQueryOptions) & QueryOptions, const [TArray](API\Runtime\Core\Containers\TArray)< [FString](API\Runtime\Core\Containers\FString) > & ExternalIds, [TArray](API\Runtime\Core\Containers\TArray)< FUniqueNetIdPtr > & OutIds )